Effects of Nd on microstructure and mechanical properties of as-cast Mg-12Gd-2Zn-xNd-0.4Zr alloys with stacking faults

In order to study the effects of Nd addition on microstructure and mechanical properties of Mg-Gd-Zn-Zr alloys,the microstruc-ture and mechanical properties of the as-cast Mg-12Gd-2Zn-xNd-0.4Zr(x=0,0.5wt%,and 1wt%)alloys were investigated by using optical microscope,scanning electron microscope,X-ray diffractometer,nano indentation tester,microhardness tester,and tensile testing machine.The results show that the microstructures mainly consist ofα-Mg matrix,eutectic phase,and stacking faults.The addition of Nd plays a significant role in grain refinement and uniform microstructure.The tensile yield strength and microhardness increase but the compression yield strength decreases with increasing Nd addition,leading to weakening tension-compression yield asymmetry in reverse of the Mg-12Gd-2Zn-xNd-0.4Zr alloys.The highest ultimate tensile strength(194 MPa)and ultimate compression strength(397 MPa)are obtained with 1wt%Nd addition of the alloy.

Effect of Combined Application of Boron and Molybdenum Microelement Fertilizer on Cowpea Yield and Quality

Through field plot experiment,we research the influencing factors of cowpea yield and quality after applying boron and molybdenum microelement fertilizer. Results show that the application of boron and molybdenum microelement fertilizer can significantly increase the yield and improve the quality of cowpea. Compared with the control,yield per mu increases by 5. 08- 18. 86%; N content increases by 4. 27%-11. 28%; P content increases by 2. 13%- 13. 57%; K content increases by 2. 00%- 18. 48%; crude protein increases by 4. 16%-19. 94%; vitamin C increases by 2. 71%- 11. 79%; nitrate content decreases by 5%- 15%. Besides,it is better to combine boron with molybdenum than to use each of them separately.

Spatial and Temporal Variability of Soil Organic Matters in Se-rich Areas of Hainan Island in Recent 30 Years

[Objectives] The aim was to reveal the distribution of soil organic matter content in cultivated land in the Se-rich areas of Hainan in 1980and 2010, so as to provide reference for the study on the evolution of soil organic matter content.[Methods] With the combination of field investigation with indoor analysis, the characteristics of organic matter content in the Se-rich areas of Hainan in 1980 and 2010 was revealed by means of spatial analysis, and the differences were analyzed.[Results] In the last 30 years, the proportion of 20-30 g/kg of soil organic matter content in the Se-rich areas of Hainan was reduced, but the content of soil organic matter in the area generally increased. The average value of the content of organic matter in the area was increased from 25.3 g/kg in the 1980s to 28.1 g/kg, but its spatial distribution was uneven.[Conclusions] The farmers should be guided to change the fertilization structure, and attention should be paid to the application of organic fertilizer, so as to improve the soil organic matter content.

Hainan; Nandu River; Soil nutrient; Spatial distribution

[Objectives] Within a research area on basin scale, soil nutrient distribution characteristics and main causes were analyzed, to provide a basis for soil nutrient management on basin scale.[Methods] With the Nandu River Basin of Hainan Island as the research area, by means of geostatistics and spatial analysis methods, the distribution available of soil pH, organic matter, alkali-hydrolyzale nitrogen, available phosphorus, available potassium and available trace elements were studied.[Results] The cultivated land in the Nandu River Basin of Hainan Province is overall acidic, with an average pH of 5.2. The soil organic matter content is overall lower, and its spatial differences are also significant. Soil alkali-hydrolyzable nitrogen, exchangeable calcium and exchangeable magnesium content are at a medium level, but the soil lacks available phosphorus and available potassium.[Conclusions] The differences in pH within the research area might be related to parent materials distribution and fertilizer applications. The main reasons for the low soil organic matter content are inadequate and uneven input of organic fertilizer and high-temperate rainy climate. The lack of soil phosphorus and potassium is mainly caused by unreasonable fertilizer application and climatic and terrain factors.